Notre Dame de Paris

Construction began on this Gothic cathedral in 1163 and continued for nearly 200 years. If you have any interest in history or architecture (or religion, for that matter), then Notre Dame is a must-see. When the Gothic-style thinner walls became too high, the famous flying buttresses were added for support. Inside the cathedral, the sculptures and stained glass are beautiful and definitely worth seeing. I was part of a tour group when I visited Notre Dame, and I found their guidance very helpful.